The present invention relates generally to radiant energy transmission devices, and in particular, to transmission devices having opposing reflective side walls operable in the concentrative mode whereby energy incident on an entrance area is directed to and concentrated on an exit area of smaller area than the entrance area. In a publication, Solar Energy, Vol. 16, No. 2, pages 89-95 (1974), in U.S. Pat. Nos. 3,923,381, 3,957,031 and 4,002,499 of Winston and in prior application Ser. No. 663,590, filed Mar. 3, 1976, there are described techniques for generating the ideal side wall contour for such a collector or transmission device. In a subsequent publication, Applied Optics, Vol. 15, No. 2, pages 291-292, Feb. 1976, there is described the application of the principles disclosed in the above art relating to ideal reflective side wall contour to transmitting and guiding surfaces at the interface of homogeneous media of differing indices of refraction for radiant energy. To the extent these items contain "essential material" necessary to support the claims hereof or indicate background, they are expressly incorporated by reference herein.
The devices employing these principles cited in the above art characterized by the side wall contour being determined by the definition that extremal rays incident on the wall are directed to be incident on the exit surface at a predetermined angle which is equal to or less than 90 degrees. In all these cases, however, all extremal rays are equally refracted between their passage between the entrance aperture, the side walls and the exit aperture. No consideration was given in the above to unequal refraction of extremal rays.
For certain concentrations, the prior art devices tend to have relatively high side walls with respect to the entrance area. Since side wall length contributes greatly to the cost of the device, the prior art technique for reducing side wall length is to truncate the device and simply do without the upper portions of the ideal reflective side wall. This may be done since the upper portions do not contribute a major portion of the concentrating ability of such devices. However, for certain uses all concentration is desirable and a fully ideal device would be desirable. In addition, the solid dielectric medium having total internal reflection may become quite expensive due to the entire area of the collector between the reflecting side walls being of an expensive dielectric material. It is therefore an object of this invention to provide an improved radiant energy direction device.
Another object of this invention is to provide an improved radiant energy concentration and collection device.
Another object of this invention is to provide a solar collector having a refractive element and an ideally contoured reflective wall.
Another object of this invention is to provide a solid solar concentrator of simplified construction utilizing cheaper materials than prior art devices.